Electrolytic process of making photosensitive mosaic screens



p 1942. R. KOLLER 2,296,616

ELECTROLYTIC PROCESS OF MAKING A PHOTO-SENSITIVE MOSAIC SCREEN Filed Feb. 1, 1939 SEIVJIT/Z/A/G SILVER LAYER 0/- 046670 J 4 j ALUMINUM 0x/a-- N Q L\\ I l ,1 O

Ihventor: Lewis R. Koller,

b fl j d y His Attorhey.

Patented Sept. 22, 1942 ELECTROLYTIC PROCESS OF MAKING PHO- TOSENSITIVE MOSAIC SCREENS Lewis B. Koller, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York v Application February 1, 1939, Serial No. 254,070

3 Claims.

My invention relates to photo-sensitive mosaic electrode structures or screens of the type used in cathode ray transmitter tubes employed in the television art. Broadly, the function of such tubes whereby an optical image thrown on the mosaic screen is scanned by the cathode ray of the tube and electrical impulses are produced corresponding to the light and shade of the image is now too well known to require a description thereof.

One object of my invention is to provide an improved and inexpensive process for the manufacture of the mosaic electrodes or screens for such tubes. Another object is the provision of the improved construction of the mosaic electrode or screen which results from that process.

My invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 is a perspective view drawn to an enlarged scale oi! a mosaic electrode or screen constructed in accordance with my invention and Fig. 2 is a cross section of a fragmentary portion thereof drawn to a still larger scale.

The mosaic electrode or mosaic screen as I prefer to call it has a conducting base comprising the aluminum plate I in contradistinction to other-well known forms of such screens having insulating bases. On a face of this plate I electrolytically oxidize a film represented at 2. The aluminum oxide film thus produced presumably is of uniform thickness, the thickness being easily controlled, but I may find it desirable' for the purpose of obtaining certain particular effects to produce a film of a variable thickness. I coat the aluminum oxide film with silver shown at 3, for example by sputtering a silver film thereon and I then heat the aluminum plate with the film thereon to a temperature of the order of 400 C. As a result of this heat treatment a network of cracks represented at 4 is formed in the aluminum oxide film thereby producing a myriad of discrete islands 5 having diameters of the order of one one-thousandth of an inch. Finally, the silver on the tops of the islands thus formed is sensitized, for example with caesium.-

In a screen constructed'in accordance with my invention it will'be seen that the spaces between the elements of the mosaic are bridged by a metallic conductor and hence will be at a deiinitely controlled potential. As a result a more uniform field distribution is obtained than is possible withcertain well known forms of screens having silver globules on a mica background.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The process of forming a photo-sensitive mosaic screen which comprises electrolytically oxidizing an aluminum base, producing a silver coating on the oxide, heating the base member to cause the oxide thereon to become separated into discrete islands and sensitizing the silver with a photo-sensitive material.

2. The process of forming a photo-sensitive mosaic screen which comprises electrolytically oxidizing the surface of an aluminum base plate, depositing silver on the oxide, heating the base plate to a temperature of the order of 400 C. to cause the oxide and the silver deposit thereon to separate into discrete islands and finally sensitizing the silver with a photo-sensitive material.

3. The process of forming a photo-sensitive mosaic screen which comprises electrolytically producing an oxide film on an aluminum plate, sputtering a silver film on the oxide film, heating the plate and films to cause the oxide film to crack into small segregated islands and finally sensitizing the silver film with a photo-sensitive material.

LEWIS R. KOLLER. 

